The present invention relates to an automatic tool changing apparatus for machine tools of the type controlled automatically such as NC machine tools.
With this type of machine tools, an automatic tool changing apparatus, selects the required tool from among a large number of tools accommodated in a magazine proper, supplies the selected tool to the spindle, removes the used tool from the spindle and changes the used tool for the required tool for the next machining operation, must be simple in construction and capable of rapidly performing smooth and positive operations. From the standpoint of operating efficiency and safety, it is also required that the working space is not reduced by the stock tools and the standby tools and that a sufficient working area is maintained. However, these requirements have not been necessarily met satisfactorily by conventional automatic tool changing apparatus. For instance, where the spindle axis and the tool axis of the magazine proper cross each other at right angles with a predetermined spacing therebetween, the tool of the magazine proper is first subjected to a so-called pot-down at the tool changing station. Then, the tool is picked up from the pot with a suitable clamping member, rotated through a suitable angle while being moved horizontally so as to align the tool axis with the spindle axis and then inserted into the spindle. In this case, while the pot-down maintains the spindle axis and the tool axis parallel to each other, making it possible to perform subsequent operations relatively easily, it is necessary to sequentially control two stages of operation, i.e., the pot-down operation of the magazine proper and the three-dimensional tool changing operation of the clamping member with the result that not only is the overall construction complicated, but also the number of tools which can be accommodated in the magazine proper is relatively small. There is another disadvantage that any attempt to increase the number of tools lengthens the magazine proper rearward and increases the installation space of the machine tool.
On the other hand, to extend a part of the magazine proper toward above the bed is not desirable from the standpoint of operating efficiency and safety, even though the tool changing can be made easier.
It will thus be seen that to ensure the desired smooth and positive operation of an automatic tool changing apparatus and to ensure the desired operating efficiency and safety are contradictory to each other in some respect, and, moreover, they will be affected greatly in dependence on the arrangement and construction of the magazine proper, thus tending to govern the destiny of this type of machine tool.